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Janne Sundell - One of the best experts on this subject based on the ideXlab platform.
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Voles and Weasels in the boreal Fennoscandian small mammal community: what happens if the least Weasel disappears due to climate change?
Integrative zoology, 2019Co-Authors: Hannu Ylönen, Marko Haapakoski, Thorbjörn Sievert, Janne SundellAbstract:Climate change, habitat loss and fragmentation are major threats for populations and a challenge for individual behavior, interactions and survival. Predator-prey interactions are modified by climate processes. In the northern latitudes, strong seasonality is changing and the main predicted feature is shortening and instability of winter. Vole populations in the boreal Fennoscandia exhibit multiannual cycles. High amplitude peak numbers of voles and dramatic population lows alternate in 3-5-year cycles shortening from North to South. One key factor, or driver, promoting the population crash and causing extreme extended lows, is suggested to be predation by the least Weasel. We review the arms race between prey voles and Weasels through the multiannual density fluctuation, affected by climate change, and especially the changes in the duration and stability of snow cover. For ground-dwelling small mammals, snow provides thermoregulation and shelter for nest sites, and helps them hide from predators. Predicted increases in the instability of winter forms a major challenge for species with coat color change between brown summer camouflage and white winter coat. One of these is the least Weasel, Mustela nivalis nivalis. Increased vulnerability of wrong-colored Weasels to predation affects vole populations and may have dramatic effects on vole dynamics. It may have cascading effects on other small rodent-predator interactions and even on plant-animal interactions and forest dynamics.
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Different escape tactics of two vole species affect the success of the hunting predator, the least Weasel
Behavioral Ecology and Sociobiology, 2013Co-Authors: Sanna Mäkeläinen, Janne Sundell, Lenka Trebatická, Hannu YlönenAbstract:In the ongoing evolutionary arms race between predators and their prey, successful escape from the predator leads to the evolution of improved escape tactics in prey, but also predators become more effective in following and attacking the prey. Antipredatory behavior of prey is considered to be the strongest towards their most dangerous predators. However, prey species can differ both in vulnerability and efficiency of escape to a shared predator. We studied escape reactions of two vole species, the bank vole (Myodes glareolus) and the field vole (Microtus agrestis), under a simulated predation risk of the least Weasel (Mustela nivalis nivalis). We conducted a laboratory experiment where a vole was given a possibility to escape from a Weasel by fleeing to a horizontal tunnel or climbing the tree. Subsequently to the vole escape decision, we released a Weasel to the same tunnel system to test how the Weasel succeeded in following the vole. Weasel presence changed the behavior of voles as especially bank voles escaped by climbing. Instead, the majority of field voles fled into the ground-layer tunnel. The different escape tactics of the voles affected the success of the Weasel, because climbing voles were less often successfully followed. We suggest that the difference in escape tactics has evolved as an adaptation to different habitats; meadow-exploiting field voles using ground-level escape while bank voles living in three-dimensional forest habitat frequently use arboreal escape tactics. This is likely to lead to different habitat-dependent vulnerabilities to predation in Microtus and Myodes vole species.
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Mammalian predator-prey interaction in a fragmented landscape: Weasels and voles.
Oecologia, 2013Co-Authors: Marko Haapakoski, Janne Sundell, Hannu YlönenAbstract:The relationship between predators and prey is thought to change due to habitat loss and fragmentation, but patterns regarding the direction of the effect are lacking. The common prediction is that specialized predators, often more dependent on a certain habitat type, should be more vulnerable to habitat loss compared to generalist predators, but actual fragmentation effects are unknown. If a predator is small and vulnerable to predation by other larger predators through intra-guild predation, habitat fragmentation will similarly affect both the prey and the small predator. In this case, the predator is predicted to behave similarly to the prey and avoid open and risky areas. We studied a specialist predator's, the least Weasel, Mustela nivalis nivalis, spacing behavior and hunting efficiency on bank voles, Myodes glareolus, in an experimentally fragmented habitat. The habitat consisted of either one large habitat patch (non-fragmented) or four small habitat patches (fragmented) with the same total area. The study was replicated in summer and autumn during a year with high avian predation risk for both voles and Weasels. As predicted, Weasels under radio-surveillance killed more voles in the non-fragmented habitat which also provided cover from avian predators during their prey search. However, this was only during autumn, when the killing rate was also generally high due to cold weather. The movement areas were the same for both sexes and both fragmentation treatments, but Weasels of both sexes were more prone to take risks in crossing the open matrix in the fragmented treatment. Our results support the hypothesis that habitat fragmentation may increase the persistence of specialist predator and prey populations if predators are limited in the same habitat as their prey and they share the same risk from avian predation.
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species specific limitation of vole population growth by least Weasel predation facilitation of coexistence
Oikos, 2008Co-Authors: Elina Koivisto, Janne Sundell, Otso Huitu, Erkki KorpimäkiAbstract:Interspecific competition is usually understood as different species competing directly with each other for limited resources. However, predators can alter such competitive interactions substantially. Predation can promote the coexistence of species in a situation where it would otherwise be impossible, for example if a tradeoff between the competitive abilities and predation resistance of the prey species exists. The field vole Microtus agrestis and the sibling vole M. rossiaemeridionalis are sympatric grassland species, which compete for the same resources. At the population level sibling voles are suggested to be superior competitors to field voles, yet more vulnerable to predation. We tested the effects of predation on the two species in 0.5 ha outdoor enclosures by exposing vole populations to radio-collared freely-hunting least Weasels Mustela nivalis nivalis for three weeks. Lethal and non-lethal impacts of predation limited population densities of both species during and after the experimental period, but the effect was more pronounced in sibling voles in which population densities decreased markedly during the treatment period and even after that. Field vole population densities remained stable under Weasel predation, while densities increased in controls. Survival in both species was lower in treatment populations compared to controls, but the effect tended to be more pronounced in sibling voles and in females of both species. The average mass of adults in both species declined in the treatment populations. These results suggest that predation by least Weasels can limit vole populations locally, even during favourable summer conditions, and have extended negative effects on the dynamics of vole populations. In addition, predation alleviated interspecific competition between the vole species and is, therefore, a potential factor enabling the coexistence of them.
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large scale spatial and temporal patterns in population dynamics of the stoat mustela erminea and the least Weasel m nivalis in finland
Oikos, 2006Co-Authors: Paavo Hellstedt, Janne Sundell, Pekka Helle, Heikki HenttonenAbstract:The stoat and the least Weasel are specialist predators of small rodents, and therefore their numbers are likely to depend on the availability of voles. These small predators are ecologically alike, but they differ somewhat in their diet. The stoat is larger in size than the least Weasel and therefore capable of using a wider variety of prey species, while the least Weasel is more restricted to small mammals. Voles in northern Fennoscandia exhibit cyclic dynamics of 3-5 years with large-scale spatial synchrony and geographical trends in cycle length and amplitude. We predicted that the cyclic dynamics of voles are reflected in the dynamics of their predators with slight differences between the stoat and the least Weasel. In this study we use snow-tracking data to characterize the dynamics of small mustelids. The data were collected from different parts of Finland using permanent triangle-shaped census routes of 12 km in 1989 to 2003. Population fluctuations of small mustelids were generally multiannually periodic and in synchrony over large areas, but we did not find any clear geographical gradient in the attribute of small mustelid dynamics comparable to those observed in vole population fluctuations. Instead, we found a similar decreasing temporal trend in the abundances of both species as has been recently reported for voles.
Hannu Ylönen - One of the best experts on this subject based on the ideXlab platform.
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Voles and Weasels in the boreal Fennoscandian small mammal community: what happens if the least Weasel disappears due to climate change?
Integrative zoology, 2019Co-Authors: Hannu Ylönen, Marko Haapakoski, Thorbjörn Sievert, Janne SundellAbstract:Climate change, habitat loss and fragmentation are major threats for populations and a challenge for individual behavior, interactions and survival. Predator-prey interactions are modified by climate processes. In the northern latitudes, strong seasonality is changing and the main predicted feature is shortening and instability of winter. Vole populations in the boreal Fennoscandia exhibit multiannual cycles. High amplitude peak numbers of voles and dramatic population lows alternate in 3-5-year cycles shortening from North to South. One key factor, or driver, promoting the population crash and causing extreme extended lows, is suggested to be predation by the least Weasel. We review the arms race between prey voles and Weasels through the multiannual density fluctuation, affected by climate change, and especially the changes in the duration and stability of snow cover. For ground-dwelling small mammals, snow provides thermoregulation and shelter for nest sites, and helps them hide from predators. Predicted increases in the instability of winter forms a major challenge for species with coat color change between brown summer camouflage and white winter coat. One of these is the least Weasel, Mustela nivalis nivalis. Increased vulnerability of wrong-colored Weasels to predation affects vole populations and may have dramatic effects on vole dynamics. It may have cascading effects on other small rodent-predator interactions and even on plant-animal interactions and forest dynamics.
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Different escape tactics of two vole species affect the success of the hunting predator, the least Weasel
Behavioral Ecology and Sociobiology, 2013Co-Authors: Sanna Mäkeläinen, Janne Sundell, Lenka Trebatická, Hannu YlönenAbstract:In the ongoing evolutionary arms race between predators and their prey, successful escape from the predator leads to the evolution of improved escape tactics in prey, but also predators become more effective in following and attacking the prey. Antipredatory behavior of prey is considered to be the strongest towards their most dangerous predators. However, prey species can differ both in vulnerability and efficiency of escape to a shared predator. We studied escape reactions of two vole species, the bank vole (Myodes glareolus) and the field vole (Microtus agrestis), under a simulated predation risk of the least Weasel (Mustela nivalis nivalis). We conducted a laboratory experiment where a vole was given a possibility to escape from a Weasel by fleeing to a horizontal tunnel or climbing the tree. Subsequently to the vole escape decision, we released a Weasel to the same tunnel system to test how the Weasel succeeded in following the vole. Weasel presence changed the behavior of voles as especially bank voles escaped by climbing. Instead, the majority of field voles fled into the ground-layer tunnel. The different escape tactics of the voles affected the success of the Weasel, because climbing voles were less often successfully followed. We suggest that the difference in escape tactics has evolved as an adaptation to different habitats; meadow-exploiting field voles using ground-level escape while bank voles living in three-dimensional forest habitat frequently use arboreal escape tactics. This is likely to lead to different habitat-dependent vulnerabilities to predation in Microtus and Myodes vole species.
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Mammalian predator-prey interaction in a fragmented landscape: Weasels and voles.
Oecologia, 2013Co-Authors: Marko Haapakoski, Janne Sundell, Hannu YlönenAbstract:The relationship between predators and prey is thought to change due to habitat loss and fragmentation, but patterns regarding the direction of the effect are lacking. The common prediction is that specialized predators, often more dependent on a certain habitat type, should be more vulnerable to habitat loss compared to generalist predators, but actual fragmentation effects are unknown. If a predator is small and vulnerable to predation by other larger predators through intra-guild predation, habitat fragmentation will similarly affect both the prey and the small predator. In this case, the predator is predicted to behave similarly to the prey and avoid open and risky areas. We studied a specialist predator's, the least Weasel, Mustela nivalis nivalis, spacing behavior and hunting efficiency on bank voles, Myodes glareolus, in an experimentally fragmented habitat. The habitat consisted of either one large habitat patch (non-fragmented) or four small habitat patches (fragmented) with the same total area. The study was replicated in summer and autumn during a year with high avian predation risk for both voles and Weasels. As predicted, Weasels under radio-surveillance killed more voles in the non-fragmented habitat which also provided cover from avian predators during their prey search. However, this was only during autumn, when the killing rate was also generally high due to cold weather. The movement areas were the same for both sexes and both fragmentation treatments, but Weasels of both sexes were more prone to take risks in crossing the open matrix in the fragmented treatment. Our results support the hypothesis that habitat fragmentation may increase the persistence of specialist predator and prey populations if predators are limited in the same habitat as their prey and they share the same risk from avian predation.
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WeaselS’ (MUSTELA NIVALIS NIVALIS) PREFERENCE FOR OLFACTORY CUES OF THE VOLE (CLETHRIONOMYS GLAREOLUS)
Ecology, 2003Co-Authors: Hannu Ylönen, Janne Sundell, Raisa Tiilikainen, Jana A. Eccard, Taina J. HorneAbstract:Many studies on life history strategies of small mammals under predation risk are based on assumptions that mammalian predators use scent marking from prey in searching and hunting. This is especially true for small mustelids hunting in the tunnels and cavities of their prey. It is assumed that Weasels use the estrous signs of female voles as hunting cues, which exposes such females to a more pronounced risk of predation. We studied the preferences of 57 least Weasels (Mustela nivalis nivalis) toward odor cues from four different reproductive categories of the bank vole (Clethrionomys glareolus). In the first experiment, Weasels selected clearly for vole odors over clean bedding in a Y-maze arena. The second experiment demonstrated that there was no difference in Weasel preference between estrous and pregnant or lactating females. Thirdly, there was no preference for odors from dominant vs. subordinate males. Finally, we offered Weasels a dyadic choice between olfactory signs of six possible combinations ...
Erkki Korpimäki - One of the best experts on this subject based on the ideXlab platform.
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The predation risks of interspecifi c eavesdropping: Weasel-vole interactions
2010Co-Authors: Nelika K. Hughes, Erkki Korpimäki, Peter B. BanksAbstract:Competing species benefi t from eavesdropping on each other’s signals by learning about shared resources or predators. But conspicuous signals are also open to exploitation by eavesdropping predators and should also pose a threat to other sympatric prey species. In western Finland, sibling voles Microtus rossiameridionalis and fi eld voles M. agrestis compete for food and space, and both species rely upon scent marks for intraspecifi c communication. Both vole species are prey to a range of terrestrial scent hunting predators such as least Weasels, however, the competitively superior sibling voles are taken preferentially. We tested in large out-door enclosures whether fi eld voles eavesdrop on the signals of its competitor, and whether they behave as though this eavesdropping carries a risk of predation. We presented fi eld voles with scent marks from unknown conspecifi cs and sibling voles and measured their visitation, activity and scent marking behaviours at these scents under high (Weasel present) and low (Weasel absent) predation risk. Field voles readily visited both fi eld and sibling vole scents under both high and low predation risk; however their activity at sibling vole scent marks declined signifi cantly under increased predation risk. In contrast, predation risk did not aff ect fi eld voles’ activity at conspecifi c scents. Th us, fi eld voles were compelled to maintain eavesdropping on heterospecifi c scents under an increased risk of predation, however they compensated for this additional risk by reducing their activity at these risky scents. Scent marking rates declined signifi cantly under high predation risk. Our results therefore reveal a hidden complexity in the use of social signals within multi-species assemblages that is clearly sensitive to the potential for increased predation risk. Th e predation risks of interspecifi c eavesdropping demonstrated here represents a signifi cant generalisation of the concept of associational susceptibility.
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species specific limitation of vole population growth by least Weasel predation facilitation of coexistence
Oikos, 2008Co-Authors: Elina Koivisto, Janne Sundell, Otso Huitu, Erkki KorpimäkiAbstract:Interspecific competition is usually understood as different species competing directly with each other for limited resources. However, predators can alter such competitive interactions substantially. Predation can promote the coexistence of species in a situation where it would otherwise be impossible, for example if a tradeoff between the competitive abilities and predation resistance of the prey species exists. The field vole Microtus agrestis and the sibling vole M. rossiaemeridionalis are sympatric grassland species, which compete for the same resources. At the population level sibling voles are suggested to be superior competitors to field voles, yet more vulnerable to predation. We tested the effects of predation on the two species in 0.5 ha outdoor enclosures by exposing vole populations to radio-collared freely-hunting least Weasels Mustela nivalis nivalis for three weeks. Lethal and non-lethal impacts of predation limited population densities of both species during and after the experimental period, but the effect was more pronounced in sibling voles in which population densities decreased markedly during the treatment period and even after that. Field vole population densities remained stable under Weasel predation, while densities increased in controls. Survival in both species was lower in treatment populations compared to controls, but the effect tended to be more pronounced in sibling voles and in females of both species. The average mass of adults in both species declined in the treatment populations. These results suggest that predation by least Weasels can limit vole populations locally, even during favourable summer conditions, and have extended negative effects on the dynamics of vole populations. In addition, predation alleviated interspecific competition between the vole species and is, therefore, a potential factor enabling the coexistence of them.
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Functional response of the least Weasel, Mustela nivalis nivalis
Oikos, 2000Co-Authors: Janne Sundell, Kai Norrdahl, Erkki Korpimäki, Ilkka HanskiAbstract:We investigated the functional response of the least Weasel (Mustela nivalis nivalis) in a series of experiments conducted in large outdoor enclosures (0.5 ha). Radiocollared Microtus voles were released in the enclosures at different densities (4, 8, 16 and 100/ha) three days before the release of a radiocollared Weasel. During the three-day experiment every vole killed was replaced with another one as soon as possible to retain constant prey density. The results demonstrated type II functional response with the predation rate reaching 50% of the asymptotic rate at a vole density of 15 individuals per ha. More voles were killed at the highest densities than would be expected from the known energy demands of Weasels. Female and male voles were killed in proportion to their abundances in the enclosures, and no difference in predation risk was detected between voles released in the enclosure before the Weasel (residents) and during the experiment (transients).
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microhabitat use and behavior of voles under Weasel and raptor predation risk predator facilitation
Behavioral Ecology, 1996Co-Authors: Erkki Korpimäki, Vesa Koivunen, Hani HakkarainenAbstract:An example of predator facilitation is that a microhabitat shift in a prey species induced by one predator increases the probability of the prey falling victim to other predators. Least Weasels (Mustela nivalis) hunt in dense plant cover, whereas kestrels (Falco tinnunculus) hunt in habitats with sparse plant cover. Field voles (Microtus agrestis), the main food of Weasels and kestrels, prefer open country with a high grass layer. We simulated a multipredator environment in an aviary (3.0 X 4.8 X 2.2 m) to find out whether predator facilitation plays a role in the interactions between voles, small mustelids, and raptors. In each replicate, we placed a field vole in a pen including sides of high and low grass layers (cover and open). In a predator-free situation, voles preferred cover but shifted to open when a Weasel was introduced to cover. In the presence of a kestrel, voles occupied cover and decreased their mobility. In the presence of a Weasel plus a kestrel, voles behaved as under the kestrel risk alone. Therefore, in these aviary circumstances, voles perceived the kestrel risk as greater than the Weasel risk. Predator facilitation in the assemblage of predators subsisting on rodent prey may contribute to the crash of the four-year vole cycle: microhabitat shift due to an avoidance of Weasel jaws may drive voles to raptor talons. Key mords: antipredatory behavior, field vole, four-year vole cycle, kestrel, least Weasel, microhabitat shift, predator facilitation. [Behav Ecol 7:30-34 (1996)]
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Responses of stoats and least Weasels to fluctuating food abundances: is the low phase of the vole cycle due to mustelid predation?
Oecologia, 1991Co-Authors: Erkki Korpimäki, Kai Norrdahl, Tuija Rinta-jaskariAbstract:We studied responses of stoats and least Weasels to fluctuating vole abundances during seven winters in western Finland. Density indices of mustelids were derived from snow-tracking, diet composition from scat samples, and vole abundances from snap-trapping. Predation rate was estimated by the ratio of voles to mustelids and by the vole kill rate by predators (density of predator x percentage of voles in the diet). We tested the following four predictions of the hypothesis that small mustelids cause the low phase of the microtine cycle. (1) The densities of predators should lag well behind the prey abundances, as time lags tend to have destabilizing effects. The densities of stoats fluctuated in accordance with the vole abundances, whereas the spring densities of least Weasels tracked the vole abundances with a half-year lag and the autumn densities with a 1-year lag. (2) Predators should not shift to alternative prey with declining vole densities. The yearly proportion of Microtus voles (the staple prey) in the diet of stoats varied widely (range 16-82%) and was positively correlated with the winter abundance of these voles. In contrast, the same proportion in the food of least Weasels was independent of the vole abundance. (3) The ratio of voles to small mustelids should be smallest in poor vole years and largest in good ones. This was also observed. (4) Vole densities from autumn to spring should decrease more in those winters when vole kill rates are high than when they are low. The data on least Weasels agreed with this prediction. Our results from least Weasels were consistent with the predictions of the hypothesis, but stoats behaved like "semi-generalist" predators. Accordingly, declines and lows in the microtine cycle may be due to least Weasel predation, but other extrinsic factors may also contribute to crashes.
Xavier Lambin - One of the best experts on this subject based on the ideXlab platform.
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Body size and habitat use of the common Weasel Mustela nivalis vulgaris in Mediterranean farmlands colonised by common voles Microtus arvalis
Mammal Research, 2019Co-Authors: Francois Mougeot, Beatriz Arroyo, Xavier Lambin, Juan José Luque-larenaAbstract:Small mustelids such as Weasels are highly specialized predators of small rodents. Their diminutive size allows hunting for prey underground, but also means that they are “bite-sized” predators, preyed upon by other larger predators. Habitat use by Weasels is therefore expected to depend not only on prey abundance, but also on predation risk. We report here on the body size and habitat use of common Weasels Mustela nivalis vulgaris captured in intensive farmlands of northwest Spain during 2009–2015. We show that Weasels’ capture rate was higher in field margins than in other habitats (cereal and alfalfa fields, fallows) irrespective of season. All small mammals (common vole, wood mouse, Algerian mouse, and greater white-toothed shrew) were consistently more frequently captured in field margins than other habitats. Weasel capture rate in each habitat was proportional to that of prey in these (alfalfa > fallows > cereal), except for field margins, which were used more intensively than expected from prey capture rate. Weasel capture rate was 37% lower in areas provided with nest boxes to increase local raptor abundance, a reduction that occurred in all habitats and was significant when correcting for prey capture rate. Weasel habitat use reflected a trade-off between prey abundance (bottom-up control) and predation risk (top-down control), with a preferential use of field margins that offer not only more prey but also permanent vegetation cover and protection from avian predators throughout most of the annual crop cycles. Weasel and vole head width data show that voles are not safe underground from smaller female Weasels and that burrow entrances were wide enough for Weasels to escape underground from predators. In NW Spain, common voles are a main farmland pest causing significant impacts. We discuss the implications of current vole control measures for Weasels in areas recurrently affected by vole outbreaks.
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Movement patterns of a specialist predator, the Weasel Mustela nivalis exploiting asynchronous cyclic field vole Microtus agrestis populations
Acta Theriologica, 2007Co-Authors: Miriam J. Brandt, Xavier LambinAbstract:We investigated habitat selection and movement characteristics of male WeaselsMustela nivalis Linnaeus, 1766 during the breeding season through radio-telemetry in Kielder Forest (KF) in order to assess how Weasel movement is influenced by prey dynamics, mate searching and predation risk, and whether the scale of Weasel movement corresponds to the spatial scale of the asynchronous, multi-annual vole population cycles observed in KF. Weasels used habitats with a high proportion of grass cover to a much larger extend than habitats with less grass cover and moved through the latter habitats faster and / or straighter. Habitats with high amounts of grass cover also had the highest field vole abundance, although total rodent abundance did not differ between habitats. The selection of this habitat by Weasels might reflect Weasels preferring field voles as prey or avoiding habitats with little grass cover and high intraguild predation risk. Five out of 8 male Weasels radio-tracked had low day-to-day site fidelity and moved between different clear cuts. Three other males were resident in a single clear cut. This variation may reflect mate searching by male Weasels. The observation that most Weasels (5 out of 8) roamed over large areas and the scale of their dispersal potential suggests, that if they regulated vole populations, they should have a greater synchronising effect on the spatial scale of vole population dynamics than what is observed in vole populations in KF.
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the impact of Weasel predation on cyclic field vole survival the specialist predator hypothesis contradicted
Journal of Animal Ecology, 2002Co-Authors: Isla M. Graham, Xavier LambinAbstract:Summary 1. The delayed density-dependent predation of specialists such as Weasels ( Mustela nivalis L.) may result in cycles in the abundance of their prey. We estimated the demographic impact of Weasel predation on field-vole ( Microtus agrestis L.) survival using capture‐recapture data from a large-scale, replicated predator-manipulation experiment conducted in six unfenced populations in Kielder Forest, northern England. The density of Weasels was experimentally reduced through continuous live-trapping in the three removal populations. Field-vole survival was compared between paired removal and control populations during the increase, peak and decline phases of a vole population cycle. Apparent survival and recapture probabilities were estimated using open population Cormack-Jolly Seber models. 2. Field-vole survival varied extensively both spatially between populations and temporally, being highest in the late autumn and over winter and lowest each year in spring and early summer. Patterns of variation in male and female survival were similar between populations over time, but there was independent spatial and temporal variation between adults and juveniles. Variation in Weasel abundance explained 18% of this independent spatial and temporal variation between adult and juvenile field-vole survival. 3. The average increase in annual vole survival resulting from Weasel removal over the 2-year period was 27% and 25% for adult male and female field voles, respectively. Decreased Weasel abundance increased adult field-vole survival. Adult-vole survival in the absence of Weasels was predicted to be approximately 8% higher than in the presence of one Weasel per 4‐5 ha. Surprisingly, Weasel removal resulted in lowered juvenile fieldvole survival, possibly reflecting increased emigration or mortality due to infanticide. A simple two age-class demographic model indicated that the decrease in juvenile survival in response to reduced Weasel predation pressure did not fully compensate for the increase in adult survival. 4. As Weasel numbers fluctuated seasonally, with highest Weasel densities occurring in late summer and autumn and little spring to spring variation, the impact of Weasel removal on field-vole survival was greatest during the breeding season. However, vole population-growth rates were unrelated to adult survival at that time and correspondingly no divergence was observed between the trajectories of control and removal vole populations even when Weasel numbers were greatest in control sites. In contrast, vole population-growth rates were closely correlated with survival during the non-breeding season. Nevertheless all control and removal populations experienced a cyclic decline in winter 1999‐2000 in spite of the increased adult survival in experimental treatments. 5. We conclude that the impact of Weasel predation on field-vole survival was neither sufficient nor necessary to initiate and drive the cyclic decline of field-vole populations in Kielder Forest.
Stephen Harris - One of the best experts on this subject based on the ideXlab platform.
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Population biology of stoats ( Mustela erminea ) and Weasels ( Mustela nivalis ) on game estates in Great Britain
Journal of Applied Ecology, 2002Co-Authors: Robbie A Mcdonald, Stephen HarrisAbstract:Summary 1. British gamekeepers commonly trap and shoot stoats and Weasels in order to increase the abundance of game. We provide details of the population biology of 822 stoats and 458 Weasels collected on 25 game estates and use simple population models to assess the effects of culling. 2. Seventy-one per cent of stoats and 94% of Weasels were trapped, while 26% of stoats and 5% of Weasels were shot. While trapped samples exhibited typically male-biased sex ratios, the sex ratio of shot stoats was even. Eight of 305 female stoats and six of 77 female Weasels were visibly pregnant, with mean litters of 9·0 and 6·2 embryos, respectively. Median ages at death were 11·6 and 8·0 months for male and female stoats, respectively, and 9·3 and 9·2 months for male and female Weasels. Male and female stoats, but not male and female Weasels, had significantly different rates of survival. 3. Model Weasel populations continued to increase ( λ = 1·35) despite culling as a result of high productivity when sufficient food was available. Model stoat populations declined slightly ( λ = 0·95), probably as a result of concerted culling effort when young stoats were dependent on maternal survival. This suggests that persistence of culled stoat populations may depend on immigration. 4. To reduce stoat populations without affecting the survival of dependent juveniles, culling effort could be focused on trapping females in late winter and shooting females in early spring, where landscape and climate permit. For control of Weasel populations, trapping effort should be, and in practice often is, focused on late spring, following a period of high natural mortality. 5. High rates of immigration mean that culling by gamekeepers will not ordinarily lead to any long-term decline in actual stoat and Weasel populations. We suggest that measures taken to enhance immigration will improve the long-term status of stoats and Weasels in regions where their conservation is desirable, and whilst this persists the impact of culling will be short-lived and local.
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The diet of stoats (Mustela erminea) and Weasels (Mustela nivalis) in Great Britain
Journal of Zoology, 2000Co-Authors: Robbie A Mcdonald, Charlotte C. Webbon, Stephen HarrisAbstract:The diet of 789 stoats Mustela erminea and 458 Weasels M. nivalis collected in Great Britain between 1995 and 1997 is described from analyses of their gut contents. As a percentage frequency of occurrence, stoat diet consisted of 65% lagomorphs, 16% small rodents and 17% birds and birds' eggs. Weasel diet consisted of 25% lagomorphs, 68% small rodents, mainly Microtus agrestis , and 5% birds and birds' eggs. Male stoats ate a greater proportion of lagomorphs than females, which ate more small rodents. No differences in diet between the sexes of the Weasels were detected. The proportion of lagomorphs in the diet of both species was greatest in the spring. Both species ate more lagomorphs in the 1990s than in the 1960s as a result of increasing rabbit populations following recovery from myxomatosis. The importance of small rodents had decreased for stoats and increased for Weasels. Both species had a dietary niche that was more specialized than in the 1960s. The implications of these findings for stoat and Weasel conservation are discussed.
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the use of trapping records to monitor populations of stoats mustela erminea and Weasels m nivalis the importance of trapping effort
Journal of Applied Ecology, 1999Co-Authors: Robbie A Mcdonald, Stephen HarrisAbstract:Summary 1. Trapping and hunting records are frequently used as an index of animal abundance. This study demonstrates that these records can be misleading if sampling effort is not controlled for. 2. Mean numbers of stoats Mustela erminea and Weasels M. nivalis trapped by British gamekeepers have been decreasing since 1975 and 1961 respectively, giving rise to concern that populations of both species may be declining. However, trapping effort has not been quantified over this period. 3. A total of 203 gamekeepers in England were questioned about the trapping effort they expended and the number of stoats and Weasels they trapped in 1997. The most significant factor affecting the number of stoats and Weasels trapped was trapping effort. 4. Gamekeepers that relied on hand-rearing game birds for shooting regarded stoats and Weasels as a less serious problem, and made substantially less trapping effort, than gamekeepers that relied on wild game birds. 5. The national decline in the numbers of stoats and Weasels trapped may be the result of a decline in stoat and Weasel populations. However, the decline is equally consistent with a reduction in trapping effort, corresponding to a national increase in reliance on hand-rearing game birds for shooting. 6. When the effect of trapping effort was controlled for, the number of Weasels trapped by gamekeepers in 1997 was significantly lower in the south-west than in other regions of England and was unusually low in some local areas. 7. Trapping records can be used effectively to monitor populations of stoats and Weasels, as long as gamekeepers record the number of traps set in each month and monthly totals of animals killed. Ideally, the sex of each animal and whether it was trapped or shot should also be recorded. Similar modifications should also be made to other wildlife monitoring schemes based on trapping and hunting records.
